Method for controlling a control station, a method for controlling terminal station, a control station, a terminal station, and a computer readable storage medium

ABSTRACT

A method for controlling a control station (H 1 ) includes the steps of performing wireless connection processing ( 204 ) with a terminal station (D 1 ) and when a wireless connection is established, sending, to the wirelessly-connected terminal station (D 1 ), a capture request signal ( 205 ) for causing the terminal station to capture a control signal ( 202 ) sent by another station (H 2 ) and to return ( 207 ) information regarding the captured control signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for controlling a controlstation, methods for controlling a terminal station, a control station,a terminal station, and a computer readable storage medium.

2. Description of the Related Art

In recant years, products that employ wireless-communication schemes,such as IEEE 802.11 wireless LANs (Local Area. Network) and wireless USB(Universal Serial Bus), are emerging.

As a control method for wireless-communication systems, there is amethod in which the control station of each network controlscommunication with the terminal stations belonging to their ownrespective networks. Under such wireless-communication systems, thecontrol station periodically sends a control signal such as a beacon,and each terminal station performs various controls for wirelesscommunication based on the received control signal. Examples include thecase where a terminal station communicates with another terminal stationthat is located on the same network using wireless-communicationparameters included in the received control signal (see Japanese PatentLaid-Open No. 2002-344458), and the case where data communication isperformed using a bandwidth assigned by the control signal (JapanesePatent Laid-Open No. 2005-04530).

However, terminal stations are not always in a location in which theycan communicate with only a control station with which they desire tocommunicate. For example, there is a case where a terminal station D1,which communicates with a control station H1 of a first network, is in alocation in which it can also receive signals from a control station H2of a second network. The control station H1 and the control station H2periodically send a beacon (control signal) for controllingcommunication with the terminal station belonging to the first andsecond network.

Here, if the control station H1 is in a location in which it cannotcommunicate wish the control station H2, the control station H1 cannotrecognize the presence of the second network. Consequently, the signalssent/received over the second network may act as interference signalsduring data transmission from the control signal H1 to the terminalstation D1.

SUMMARY OF THE INVENTION

The present invention allows a control station to recognize, at anappropriate time, the existence of a communication environment beyondthe communication range of the control station.

According to one aspect of the present invention, a method forcontrolling a control station, at the control station, crises the stepsof:

determining a wireless communication status with a terminal station; and

sending, based on the wireless communication status, a capture requestsignal to cause the terminal station to capture a control signal sent byanother station and to return information regarding the captured signal.

According to another aspect of the present invention, a method forcontrolling a terminal station, at the terminal station, comprises thesteps of:

determining a wireless communication status of the terminal station; and

based on the wireless communication status, sending, to a controlstation, a signal for causing the control station to send a capturerequest signal, wherein the capture request signal is transmitted forcausing the terminal station to capture a control signal sent by anotherstation and to return information regarding the captured control signal,to the control station.

According to still another aspect of the present invention, a controlstation comprises:

a determining unit adapted to determine a wireless communication statuswith a terminal station; and

a sending unit adapted to send, based on the wireless communicationstatus, a capture request signal to cause the terminal station tocapture a control signal sent by another station and to returninformation regarding the captured signal.

According to yet another aspect of the present invention, a terminalstation comprises:

a determining unit adapted to determine a wireless communication statusof the terminal station; and

a sending unit adapted to send, to a control station, a signal forcausing the control station to send a capture request signal based onthe wireless communication status, wherein the capture request signal istransmitted for causing the terminal station to capture a control signalsent by another station and to return to the control station informationregarding the captured control signal.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an arrangement of wireless stationsaccording to embodiments of the or invention.

FIG. 2 is a diagram illustrating a sequence executed by wirelessstations according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating an internal configuration of a wirelessstation according to embodiments of the present invention.

FIG. 4 is a diagram illustrating an operation flow performed by acontrol station H1 according to Embodiment 1 of the present invention.

FIG. 5 is a diagram illustrating a sequence executed by wirelessstations according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating another sequence executed by wirelessstations according to the second embodiment of the present invention.

FIG. 7 is a diagram illustrating an operation flow performed by acontrol station accord in to the second embodiment of the presentinvention.

FIG. 8 is a diagram illustrating a sequence executed by wirelessstations according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a sequence executed by wirelessstations according to the third embodiment of the present invention.

FIG. 10 is a diagram illustrating a sequence executed by wirelessstations according to Embodiment 3 of the present invention.

DESCRIPTION OF THE EMBODIMENTS Embodiment 1

Embodiment 1 of the present invention shall be described with referenceto FIGS. 1 to 3.

FIG. 1 is a diagram illustrating an arrangement of wireless stationsaccording to Embodiment 1.

H1 and H2 denote wireless-communication control stations, and D1 denotesa terminal station. The terminal station D1 communicates with thecontrol station H1 based on various information included in a beacon(control signal) that is sent periodically from the control station H1.The beacon includes information such as a bandwidth as for datatransmission from the control station H1 to the terminal station D1, abandwidth assigned for data transmission from the terminal station D1 tothe control station H1, and the like, and the terminal station D1performs data communication using the assigned bandwidths. The controlstation H2, on the hand, is a control station that does not communicatewith the terminal station D1, and periodically sends a beacon to aterminal station (not shown) located on its own communication range.This beacon includes information such as a bandwidth assigned for datatransmission from the control station H2 to a terminal station that islocated on the communication range of the control station H2, and abandwidth assigned for data transmission from the terminal stationlocated on the communication range of the control station H2 to thecontrol station H2. Note that the term “bandwidth” used in the presentembodiment and the following embodiments refers to a time interval (timeslot) used for communication.

CA 1 and CA 2 indicate communication ranges of the control stations H1and P2, respectively. As illustrated in FIG. 1, the control at H1 cannotreceive beacons sent by the control station H2, and the control stationH2 cannot receive beacons sent by the control station H1. The terminalstation D1 is in a location in which it can receive beacons from bothcontrol stations H1 and H2.

FIG. 2 is a diagram illustrating an example of a sequence according tothe present embodiment.

The control station H1 periodically sends a connection authorizationsignal for allowing the terminal station to wirelessly connect to thecontrol station H1 (201). The control station H2 periodically sends abeacon (202). The terminal station D1 is in a location in which theterminal station D1 can also receive beacons from the control stationH2. Upon receiving the connection authorization signal (201) sent by thecontrol station H1, the terminal station D1 returns a response (207) tothe connection authorization signal (201) in order to commencecommunication with the control station H1. Upon receiving the response,the control station H1 commences connection processing for connecting tothe terminal station D1 (204).

In the present embodiment, a wireless connection is established afterthe terminal station has returned a response to the connectionauthorization signal from the control station. However, in the presentinvention, the connection processing method is not limited to anyparticular method. It is also possible to establish a wirelessconnection, or example, after the control station has returned aresponse to a connection request having been sent by the terminalstation, as in an THEE 802.11 wireless LAN. It is also possible toperform an authentication process before the connection processing.

After the connection processing for connecting to the terminal stationD1 is completed (204), the control station H1 sends, to the terminalstation D1, a signal (hereinafter referred to as “capture requestsignal”) for causing the terminal station D1 to capture a beacon sent byanother station and return information regarding the captured beacon(205). The information returned includes the content of the beaconreceived by the terminal station D1 within the period specified by thecapture request signal, the timing at which the beacon was received, andthe quality of the reception.

Upon receiving the capture request signal, the terminal station D1captures a beacon sent by another station, and monitors thecommunication environment (206). In the present embodiment, the terminalstation D1 receives a beacon (202) sent by the control station H2, andreturns information regarding the received beacon to the control stationH1 (207).

The control station H1 arranges a bandwidth in which the control stationH1 sends beacons and data to the terminal station D1 based on theinformation returned from the terminal station D1 such that thebandwidth does not overlap with the bandwidth in which the controlstation H2 sends beacons. The control station H1 then sends a beaconcontaining information regarding the arranged bandwidth to the terminalstation D1 (208), and commences wireless communication with the terminalstation D1 that has received the beacon (209).

In this manner, the control station H1 causes the terminal station D1 tomonitor the surrounding communication environment before commencingwireless communication, whereby the control station H1 can recognize thepresence of another station that is not located on its own communicationrange, but in the communication range of its communication partner, theterminal station D1. Accordingly, the control station cart assign acommunication bandwidth such that the signals sent from the anotherstation do not act as interference signals in the data communicationbetween the control station H1 and the terminal station D1. In otherwords, it is possible to prevent the beacons and data sent from thecontrol station H1 to the terminal station D1 from colliding with thebeacons sent from the control station H2.

When the control station H1 recognizes, from the information returnedfrom the terminal station D1, that the control station H2 is located ona range in which the control station H2 can communicate with theterminal station D1, the control station H1 may cause the terminalstation D1 to send a notification signal that enables the controlstation 112 to recognize the bandwidth used by the control station H1and the terminal station D1. The control station H2 can recognize thebandwidth used for the communication between the control station H1 andthe terminal station D1 by receiving the notification signal sent fromthe terminal station D1, and thus the control station H2 can assign anappropriate bandwidth as well.

FIG. 3 is a block diagram illustrating a configuration of awireless-communication apparatus 101 provided in each wireless station.If the control station H1 is a printer, for example, the control stationH1 can have a wireless-communication function in addition to a printingfunction by incorporating the wireless-communication apparatus 101.

A controller 102 of the wireless-communication apparatus 101 performsvarious controls as shall be described below.

A CPU 102 a performs wireless-communication control by executing acontrol program stored in a ROM 102 b.

The control station has a function for performing connection processingwith a terminal station and communicating with the terminal station, anda function for sending a capture request signal to the terminal stationand analyzing the communication environment surrounding the terminalstation from the content of the response to the capture request signal.The control station also has a function for generating a beaconincluding information regarding a bandwidth assigned for datacommunication and sending the beacon. The control station further has afunction for transmitting data to the terminal station based on thebandwidth information included in the beacon, and a function fordetermining whether or not the data transmission is successful by thesuccess or failure of Ack (acknowledgment signal) reception.

The control station further has a function for receiving data from theterminal station based on the bandwidth information included in thebeacon if the control station receives data successfully, the controlstation further has a function for returning an Ack, and a function fordetermining whether or not the Ack signal transmission is successful byretransmitting data from the terminal station.

Meanwhile, the terminal station has a function for performing connectionprocessing with a control station and communicating with the controlstation, and a function for capturing a beacon sent by another stationupon receiving a capture request signal from the control station andreturning information regarding the captured beacon. The terminalstation also has a function for receiving data based on bandwidthinformation included in the beacon sent from the control station, and afunction for returning an Ack if it has received the data successfully.

The terminal station also has a function for transmitting data based onthe bandwidth information included in the beacon sent from the controlstation. Furthermore, the terminal station has a function fordetermining whether or not the data transmission is successful by thesuccess or failure of Ack reception, and a function for retransmittingdata if the Ack reception has failed.

A RAM 102 c provides a working area or the like used when the CPU 102 aexecutes various controls. A wireless interface 103 wirelessly sends atransmission signal output from a controller through an antenna 104, andconverts a wireless signal received through the antenna 104 to a digitalsignal that can be processed by the controller 102.

FIG. 4 is a diagram illustrating an operation flow performed by thecontrol station H1 according to the present embodiment.

Upon establishing a wireless connection with the terminal station D1(Yes in S401), the control station H1 sends a capture request signal tothe terminal station D1 (S402). Upon receiving a response to the capturerequest signal (S403), the control station H1 arranges a bandwidthassigned for the data communication with the terminal station D1 basedon the information returned from the terminal station D1. Then, thecontrol station H1 sends a beacon including information regarding theassigned bandwidth (S404), and commences data communication with theterminal station D1 that has received the beacon (S405).

As described above, according to the present invention, the controlstation sends a capture request signal to the terminal station when awireless connection with the terminal station is established. Thecontrol station then performs control on a bandwidth for use in datacommunication with the terminal station based on the informationreturned in response to the capture request signal. Accordingly, even ifanother station is located on a range in which the control stationcannot communicate, it is possible to suppress degradation in the datacommunication quality due to an interference signal originating fromthat station.

Embodiment 2

Embodiment 2 of the present invention shall be described next. Since thearrangement of wireless stations and the block diagram illustrating aconfiguration of a wireless-communication apparatus provided in eachwireless station are the same as those in Embodiment 1 (FIGS. 1 and 3),descriptions thereof are omitted here.

FIG. 5 is a diagram illustrating an example of a sequence according tothe present embodiment. FIG. 5 illustrates a situation in which thecontrol station sends a capture request signal when the control stationcannot receive an ACE from the terminal station after the controlstation has sent data to she terminal station.

The control station H1 periodically sends a beacon (501, 504). Thebeacon includes information such as a bandwidth assigned for datatransmission from the control station H1 to the terminal station D1, abandwidth assigned for data transmission from the terminal station D1 tothe control station H1, and the like. The control station H1 and theterminal station D1 perform data communication based on the bandwidthinformation (502, 503, 505, 507).

First, based on the bandwidth information included in a beacon H1-1(501), data 1 is sent from the control station H1 to the terminalstation D1 (502). Upon receiving the data 1, the terminal station D1sends an ACK 1 to the control station H1 (503).

Next, based on the bandwidth information included in a beacon H1-2(504), data 2 is sent from the control station H1 to the terminalstation D1 (505). Here, it is assumed that the data 2 has collided witha beacon H2-1 sent from the control station H2 (506), and the terminalstation D1 could not properly receive the data 2. Consequently, theterminal station D1 does not send an ACE 2 to the control station H1(507).

If the control station H1 cannot receive an Ack 2 for a predeterminedperiod of time, the control station H1 sends a capture request signal tothe terminal station D1 (508). Upon receiving the capture requestsignal, the terminal station D1 captures a beacon sent by anotherstation, and monitors the communication environment (509). In thepresent embodiment, the terminal station D1 receives a beacon. H2-2(510) sent by the control station H2, and returns information regardingthe received beacon to the control station H1 (511).

The control station H1 arranges a bandwidth in which the control stationin sends beacons and data to the terminal station D1 based on theinformation returned from the terminal station D1 such that thebandwidth does not overlap with a bandwidth in which the control stationH2 sends beacons (506, 510, 513). The control station H1 sends a beaconH1-3 that includes information regarding the arranged bandwidth to theterminal station D1 (512), and resumes wireless communication with theterminal station D1 that has received the beacon H1-3 (514).

When the control station H1 recognizes from the information returnedfrom the terminal station D1, that the control station H2 is located ona range in which the control station H2 can communicate with theterminal station D1, the control station H1 may cause the terminalstation D1 to send a notification signal that allows the control stationH2 to recognize the bandwidth used by the control station H1 and theterminal station D1. The control station H2 can recognize the bandwidthused for the communication between the control station H1 and theterminal station D1 by receiving the notification signal sent by theterminal station D1, and thus the control station H2 can assign anappropriate bandwidth as well.

As described above, when the control station H1 cannot receive an ACK,it causes the terminal station D1 to monitor the surroundingcommunication environment, whereby the control station. H1 can recognizethe presence of another station that is not located on its owncommunication range, but is located on the communication range of itscommunication partner, the terminal station D1. Accordingly, even if thecontrol station H1 cannot detect the fact that a data collision hasoccurred with the terminal station D1, the control station H1 canperform control to assign a communication bandwidth such that no datacollision occurs after that. Normally, the control station H1retransmits data when it did not receive an ACK, but if data collisionsoccur continuously in the terminal station, the repeated transmissioncan result in a waste of bandwidth. However, the control according tothe present embodiment, makes it possible not only to avoid datacollisions immediately but also to effectively utilize bandwidth.

FIG. 6 is a diagram illustrating an example of a sequence according tothe present embodiment. FIG. 6 illustrates a situation in which thecontrol station sends a capture request signal when data isretransmitted despite the fact that the control, station has sent an ASKin response to the data received from the terminal station.

The control station H1 periodically sends a beacon (601, 604). Thebeacon includes information such as a bandwidth assigned for datatransmission from the control station H1 to the terminal station D1, anda bandwidth assigned for data transmission from the terminal station D1to the control station H1. The control station H1 and the terminalstation D1 perform data communication based on the bandwidth information(602, 603, 605, 606).

First, based on the bandwidth information included in a beacon H1-1(601), data 1 is sent from the terminal station D1 to the controlstation H1 (602). Upon receiving the data 1, the control station H1sends an ACK 1 to the terminal station D1 (603).

Next, based on the bandwidth information included in a beacon H1-2(604), data 2 is sent from the terminal station D1 to the controlstation 51 (605). Upon receiving the data 2, the control station H1sends an ASK 2 to the terminal station D1 (606). At this time, it isassumed that the ACK 2 has collided with a beacon H2-1 (607) sent fromthe control station H2, and the terminal station D1 could not receivethe ACK 2 properly.

Because the terminal station D1 could not receive the ACK 2 properly, ittransmits the data 2 again to the control station (608). If the controlstation H1 detects that the data 2 has been retransmitted despite thefact that the control station H1 returned the ACE 2, the control stationH1 sends a capture request signal to the terminal station D1 (609). Uponreceiving the capture request signal, the terminal station D1 captures abeacon sent by another station, and monitors the communicationenvironment (610). In the present embodiment, the terminal station D1receives a beacon H2-2 (611) sent by the control station H2, and returnsinformation regarding the received beacon to the control station H1(612).

The control station H1 arranges a bandwidth in which the control stationH1 sends beacons and data to the terminal station D1 based on theinformation returned from the terminal station D1 such that thebandwidth does not overlap with a bandwidth in which the control stationH2 sends beacons (607, 611, 513). The control station H1 then sends abeacon H1-3 including information regarding the arranged bandwidth tothe terminal station D1 (614), and resumes wireless communication withthe terminal station D1 that has received the beacon H1-3 (615).

When the control station H1 recognizes, from the information returned,from the terminal station D1, that the control station H2 is located onthe range in which the control station H2 can communicate with theterminal station D1, the control station H1 may cause the terminalstation D1 to send a notification signal that allows the control stationH2 to recognize the bandwidth used by the control station and theterminal station D1. The control station 52 can recognize the bandwidthused for the communication between the control station H1 and theterminal station D1 by receiving the notification signal sent by theterminal station D1, and thus the control station 112 can assign anappropriate bandwidth as well.

As described above, when data is retransmitted despite the fact that thecontrol station H1 has sent an ACK, the control station H1 causes theterminal station D1 to capture a beacon sent from another station,whereby the control station H1 can recognize the presence of anotherstation that is not located on its own communication range, but in thecommunication range of its communication partner, the terminal stationD1. Accordingly, even if the control station H1 cannot detect the factthat a data collision has occurred with the terminal station D1, thecontrol station H1 can perform control to assign a communicationbandwidth such that no data collision occurs after that.

FIG. 7 is a diagram illustrating an operation flow performed by thecontrol station H1 according to the present embodiment.

The control station H1 periodically sends a beacon including informationregarding a bandwidth to be assigned for data communication with the tostation D1 (S701). After having sent the beacon, the control station H1determines whether the bandwidth is a bandwidth for data transmission ora bandwidth for data reception (S702). The control station H1 then sendsdata to the terminal station D1 (S103), or receives data from theterminal station D1 (S710) depending on the results of thedetermination.

If the control station H1 has sent data to the terminal station D1(S703), it waits for an ACK from the terminal station D1 for apredetermined period of time. If the control station H1 receives an ACK(Yes in S704), the control station H1 continues to communicate with theterminal station D1 (S705).

If the control station H1 does not receive an ACK for as predeterminedperiod of time (No in S704), the control station H1 sends a capturerequest signal to the terminal station D1 (S706). Upon receiving aresponse to the capture request signal from the terminal station D1(S707), the control station H1 arranges a bandwidth to be assigned fordata communication with the terminal station D1 based on the informationreturned by the terminal station D1. Then, the control station H1 sendsa beacon including information regarding the arranged bandwidth (S708),and tea ones a data communication with the terminal station D1 that hasreceived the beacon (S709).

If the control station H1 has received data from the terminal station D1(S710), the control station H1 sends an ACK to the terminal station D1(S711). If the data is retransmitted from the terminal station D1 afterthe control station H1 has sent the ACK (Yes in S712), the controlstation H1 sends a capture request signal to the terminal station D1(S706). The process after S707 is the same as the process describedabove, and therefore descriptions thereof shall be omitted here. If thecontrol station H1 does not receive the retransmission data (No inS712), the control station H1 continues to communicate with the terminalstation D1 (S713).

In the foregoing, in S704, the control station H1 sends a capturerequest signal immediately after it did not receive a single ASK, but itis also possible for the control station H1 to send a capture requestsignal after it did not receive a predetermined number of ACKs afterattempting to transmit the data several times. Similarly, in S712, it isalso possible for the control, station H1 to send a capture requestsignal after attempting to send several ACKs and receivingretransmission data a predetermined number of times, rather thanimmediately after it has received retransmission data only once. It isthereby possible to prevent unnecessary capture request signals frombeing sent when the transmission/reception of an ACK is unsuccessful duenot to a data collision in the terminal station D1, but due, rather, toan error in the control station H1 or the like.

As described above, if the control station cannot receive an ACK fromthe terminal station after transmitting data to the terminal station, orif data is retransmitted despite the fact that the control station sentan ACK to the terminal station when receiving data from the terminalstation, the control station sends a capture request signal to theterminal station. The control station then performs control on abandwidth used for data communication with the terminal at based on theinformation returned in response to the capture request signal.Accordingly, even when another station is located on a range in whichthe control station cannot communicate, it is possible to suppressdegradation in the data communication quality due to an interferencesignal originating from that station.

Embodiment 3

Embodiment 3 of the present invention shall be described next. Since thearrangement of wireless stations is the same as that of Embodiment 1(FIG. 1), descriptions thereof shall be omitted here. The block diagram,illustrating a configuration of a wireless-communication apparatusprovided in each wireless station is the same as that of Embodiment 1,except that the functions described below are added in the presentembodiment.

The terminal station D1 is further provided with a function for sendinga signal (hereinafter “command 1”) for causing the control station H1 tosend a capture request signal.

The control station H1, meanwhile, is further provided with a functionfor sending a capture request signal upon receiving the command 1 fromthe terminal station D1.

FIG. 8 is a diagram illustrating an example of a sequence according tothe present embodiment.

The control station H1 periodically sends a connection authorizationsignal for allowing the terminal station to wirelessly connect to thecontrol station H1 (801). The control station H2 also periodically sendsa beacon (802). The terminal station D1 is in a location in which it canalso receive the beacon from the control station H2. Upon receiving theconnection authorization signal (801) sent by the control station H1,the terminal station D1 sends a response (803) to the connectionauthorization signal (801) to communicate with the control station H1.Upon receiving the response, the control station H1 commences connectionprocessing for connecting to the terminal station D1 (804).

In the present embodiment, a wireless connection is established afterthe terminal station has returned a response to the connectionauthorization signal from the control station. However, in the presentinvention, the connection processing method is not, limited to anyparticular method. It is also possible to establish a wirelessconnection, for example, after the control station has returned aresponse to a connection request having been sent by the terminalstation, an in an IEEE 802.11 wireless LAN. It is also possible toperform an authentication process before the connection processing.

After the connection processing for connecting to the control station H1is completed (804), the terminal station D1 sends a command 1 to thecontrol station H1 (805). Upon receiving the command 1, the controlstation H1 sends a capture request signal to the terminal station D1(806).

Upon receiving the capture request signal, the terminal station D1captures a beacon sent by another at and monitors the communicationenvironment (907). In the present embodiment, the terminal station D1receives a beacon (802) sent by the control station H2, and returnsinformation regarding the received beacon to the control station H1(808).

The control station H1 arranges a bandwidth in which the control stationH1 sends beacons and data to the terminal station D1 based on theinformation returned from the terminal station D1 such that thebandwidth does not overlap with a bandwidth in which the control stationH2 sends beacons. The control station H1 then sends a beacon containinginformation regarding the arranged bandwidth to the terminal station D1(809), and commences wireless communication with the terminal station D1that has received the beacon (810).

In this manner, the terminal station D1 sends a command 1 to the controlstation H1 after a wireless connection with control station H1 isestablished, and the control station H1 sends a capture request signalin response to the command 1. Consequently, effects similar to those ofEmbodiment 1 can be attained.

FIG. 9 is a diagram illustrating another example in which the terminalstation D1 sends a command 1. FIG. 9 illustrates a situation in whichthe terminal station D1 sends a command 1 when it cannot properlyreceive data that is sent from the control station H1.

The control station H1 periodically sends a beacon (901, 904). Thebeacon includes information such as a bandwidth assigned for datatransmission from the control station H1 to the terminal station D1, abandwidth assigned for data transmission from the terminal station D1 tothe control station H1, and the like. The control station H1 and theterminal station. D1 perform data communication based on the bandwidthinformation (902, 903, 905).

First, based on the bandwidth information included in a beacon H1-1(901), data 1 is sent from the control station H1 to the terminalstation D1 (902) been receiving the data 1, the terminal station D1sends an ACK 1 to the control station H1 (903).

Next, based on the bandwidth information included in a beacon H1-2(904), data 2 is sent from the control station H1 to the terminalstation D1 (905). At this time, it is assumed that the data 2 hascollided with a beacon H2-1 (906) sent from the control station H2, andthe terminal station D1 could not receive the data 2 properly.

If the terminal station D1 could not receive the data 2 properly, theterminal station D1 sends a command 1 to the control station H1 (907).Upon receiving the command 1, the control station H1 sends a capturerequest signal to the terminal station D1 (908). Upon receiving thecapture request signal, the terminal station D1 captures a beacon sentby another station, and monitors the communication environment (909). Inthe present embodiment, the terminal station D1 receives a beacon H2-2(910) sent by the control station H21, and returns information regardingthe received beacon to the control station H1 (911).

The control station H1 arranges a bandwidth in which the control stationin sends beacons and data to the terminal station D1 based on theinformation returned from the terminal station D1 such that thebandwidth does not overlap with a bandwidth in which the control stationH2 sends beacons (906, 910, 913). The control station H1 sends a beaconH1-3 that includes information regarding the arranged bandwidth to theterminal station D1 (912), and resumes wireless communication with theterminal station D1 that has received the beacon H1-3 (914).

In this manner, upon failure to correctly receive data from the controlstation H1, the terminal station D1 sends a command 1 to the controlstation H1, and the control station H1 sends a capture request signal inresponse to the command 1. Consequently, effects similar to those ofEmbodiment 2 can be attained.

FIG. 10 is a diagram illustrating another example in which the terminalstation D1 sends a command 1. The present embodiment describes aconfiguration in which the terminal station D1 sends a command 1 when ithas detected a beacon sent from a control station other than, itscommunication partner, the control station H1.

The control station H1 periodically sends a beacon (1001). The beaconincludes information such as a bandwidth ansa for data transmission fromthe control station H1 to the terminal station D1, a bandwidth assignedfor data transmission from the terminal station D1 to the controlstation H1, and the like. The control station H1 and the terminalstation D1 perform data communication based on the bandwidth information(1002, 1003).

If the terminal station D1 detects a beacon H2-1 sent by the controlstation H2 (1004) at this time, the terminal station D1 sends a command1 to the control station H1 (1005). Upon receiving the command thecontrol station H1 sends a capture request signal to the terminalstation D1 (1006). Upon receiving she capture request signal, theterminal station D1 captures a beacon sent by another station, andmonitors the communication environment (1007). In the presentembodiment, the terminal station D1 receives a beacon H2-2 (1008) sentby the control station H2, and returns information regarding thereceived beacon to the control station H1 (1009).

The control station H1 arranges a bandwidth in which the control stationH1 sends beacons and data to the terminal station D1 based on theinformation returned from the terminal station D1 such that thebandwidth does not overlap with a bandwidth in which the control stationH2 sends beacons (1004, 1008, 1011). The control station H1 sends abeacon H1-2 that includes information regarding the arranged bandwidthto the terminal station D1 (1010), and resumes wireless communicationwith the terminal station D1 that has received the beacon H1-2 (1012).

In this manner, upon detecting a beacon sent from the control stationH2, the terminal station D1 sends a command 1 to the control station H1,and the control station H1 sends a capture request signal in response tothe command 1. Consequently, it is possible to prevent the signals sentfrom the control station H1 to the terminal station D1 from collidingwith the beacons sent, from the control station H2.

As described above, accordion to the present embodiment, the controlstation H1 sends a capture request signal in response to the command 1sent from the terminal station D1. Even when the control at H1 does nothave a function for controlling the timing of sending a capture requestsignal as described in Embodiments 1 and 2, by adding the functiondescribed in the present embodiment to the terminal station andconfiguring the control station to be able to interpret the command 1sent from the terminal station, it is possible to attain effects similarto those of Embodiments 1 and 2.

A wireless LAN access point and a station, or a wireless USE host anddevice, can be given as examples of the control station and the terminalstation described in the above embodiments.

Embodiments 1 and 3 discuss operations performed when the terminalstation makes a new wireless connection to the control station, butthese embodiments are also applicable to the case where the terminalstation or the control station wakes up from a standby mode (i.e., whenthe mode is changed from a power-saving mode to a normal mode) and thecase where the terminal station reconnects to the control station.

It should be noted that the object of the present invention can also beachieved by supplying a system or an apparatus with a recording mediumin which a software computer program that realizes the function of theabove-mentioned embodiments is recorded, and a computer (CPU or MPU) ofthe system or apparatus loading and executing the computer programstored in the recording medium.

In this case, the computer program itself loaded from the recordingmedium realizes the function of the above-mentioned embodiments, and thepresent invention is configured of the recording medium in which thecomputer program is stored.

Examples of recording media that can be used for supplying the computerprogram include Floppy® disks, hard disks, optical, disks,magneto-optical disks, CD-ROMS, CD-Rs, magnetic tape, non-volatile typememory cards and ROMs.

The function of the above-mentioned embodiments can be realized not onlyby executing a computer program loaded by a computer. That is, the casewhere an operating system (OS) running in a computer performs part orall of the actual processing based on the instructions of the computerprogram, and the function of the above-mentioned embodiments is realizedby that processing, is included in the scope of the present invention.

Further, the present invention can also be applied in the case where thecomputer program loaded from the recording medium is written into amemory provided in a function expansion board installed in the computeror a function expansion unit connected to the computer. In such a case,a CPU or the like provided in the function expansion board or thefunction expansion unit performs part or all, of the actual processingbased on the instructions of the computer program, and the function ofthe above-mentioned embodiment is realized by that processing.

As described above, according to the embodiments given above, thecontrol station causes the terminal station to capture a beacon sent byanother station, and controls data communication with the terminalstation based on the captured information. Accordingly, even whenanother station is present in a range in which the control stationcannot communicate, the control station can recognize the presence ofthat station. By performing control on the assignment of a communicationbandwidth based on the captured information, the degradation of datacommunication quality due an interference signal originating from thestation can be suppressed.

According to the foregoing descriptions, the control station performswireless connection processing for connecting to the terminal station,and when the wireless connection is established, the control stationsends a capture request signal for causing the terminal stationwirelessly connected to the control station to capture a control signalsent by another station and return information regarding the capturedcontrol signal. Thereby, the control station can be aware of thepresence of another station that is located on a range in which thecontrol station cannot communicate, before commencing wirelesscommunication.

Further, the control station sends a control signal that includesinformation regarding a bandwidth assigned for data communication withthe wirelessly-connected terminal station, and transmits data to theterminal station in the assigned bandwidth. If the control stationcannot receive an acknowledgement signal in response to the datatransmitted, the control station sends, to the terminal station, acapture request signal for causing the terminal station to capture acontrol signal sent by another station and return information regardingthe captured control signal. Thereby, even if the control station cannotreceive an acknowledgment signal, the control station can be aware ofthe communication environment out of range of the control station.

Further, the control station sends a control signal includinginformation regarding a bandwidth assigned for data communication withthe wirelessly-connected terminal station, and returns an acknowledgmentsignal if receiving data from the terminal station in the assignedbandwidth. If the control station receives retransmission data from theterminal station after having returned the acknowledgment signal, thecontrol station sends, to the terminal station, a capture request signalfor causing the terminal station to capture a control signal sent byanother station and return information regarding be captured controlsignal. Accordingly, even if data is retransmitted despite the fact thatthe terminal station has sent an acknowledgment signal, the controlstation can be aware of the communication environment out of range ofthe control station.

Further, the control station determines a bandwidth to be assigned fordata communication with the terminal station based on the informationreturned in response to the capture request signal, and sends controlsignal including information regarding the determined bandwidth.Thereby, the control station can determine a communication bandwidththat will not interfere with the data communication of another stationlocated on a range in which the control station cannot communicate.

The information that the terminal station having received the capturerequest signal monitors includes at least one of the content of acontrol signal received by the terminal station from another station,the timing at which the signal was received, and the quality of thereception.

The terminal station performs wireless connection processing with thecontrol station having a function for sending a capture request signalfor causing the terminal station to capture a control sent by anotherstation and return information regarding the captured control signal.Upon establishing the wireless connection, the terminal station sends,to the control station, a signal for causing the control station to senda capture request signal. Thereby, the control station can send thecapture request signal based on the instruction from the terminalstation before commencing wireless communication.

The terminal station receives a control signal including informationregarding a bandwidth assigned for data communication with the controlstation from the control station having a function for sending a capturerequest signal for causing the terminal station to capture a controlsignal sent, by another station and return information regarding thecaptured control signal. If the terminal station cannot receive datafrom the control station in the assigned bandwidth, the terminal stationsends a signal for causing the control station to send a capture requestsignal. Thereby, even when the communication environment of the terminalstation is poor, the terminal station can issue an instruction to send acapture request signal, to the control station.

The terminal station also receives a control signal includinginformation regarding a bandwidth assigned for data communication withthe control at from the control station having a function for sending acapture request signal for causing the terminal station to capture acontrol signal sent by another station and return information regardingthe captured control signal. If the terminal station detects a controlsignal from a control station other than the above-mentioned control,station, the terminal station sends a signal for causing the controlstation to send a capture request signal. Thereby, when the terminalstation has detected the presence of a control station with which theterminal station does not wish to communicate, the terminal station canissue, an instruction to send a capture request signal to the controlstation.

As described above, according to the present invention, the controlstation sends a capture request signal to toe terminal station at anappropriate time, whereby the control station can recognize acommunication environment out of the range of the control station.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2007-152708, flied on Jun. 8, 2007, which is hereby incorporated byreference herein in its entirety.

1.-14. (canceled)
 15. A communication apparatus, which wirelesslycommunicates with a terminal station, comprising: a sending unitconfigured to send a predetermined signal to cause the terminal stationto return information regarding a control signal sent by anothercommunication apparatus in a case that wireless communication betweenthe communication apparatus and the terminal station failed; adetermining unit configured to determine a bandwidth to be assigned forwireless communication between the communication apparatus and theterminal station based on the information returned from the terminalstation in response to the predetermined signal; and a notifying unitconfigured to notify the determined bandwidth to the terminal station.16. The apparatus according to claim 15, wherein the wirelesscommunication between the communication apparatus and the terminalstation is determined to have failed in a case that the communicationapparatus, after transmitting data to the terminal station, fails toreceive a response signal corresponding to the data transmission fromthe terminal station.
 17. The apparatus according to claim 15, whereinthe wireless communication between the communication apparatus and theterminal station is determined to have failed in a case that thecommunication apparatus, after the communication apparatus transmits aresponse signal in response to reception of data from the terminalstation, receives said data retransmitted from the terminal station. 18.The apparatus according to claim 15, wherein the information includes atleast one of content of the control signal, reception timing of thecontrol signal and reception quality of the control signal.
 19. Acontrol method of a communication apparatus, which wirelesslycommunicates with a terminal station, said method comprising the stepsof: sending a predetermined signal to cause the terminal station toreturn information regarding a control signal sent by anothercommunication apparatus in a case that wireless communication betweenthe communication apparatus and the terminal station failed; determininga bandwidth to be assigned for wireless communication between thecommunication apparatus and the terminal station based on theinformation returned from the terminal station in response to thepredetermined signal; and notifying the determined bandwidth to theterminal station.
 20. A non-transitory computer-readable storage mediumstoring a computer program for causing a computer to perform each stepof the control method according to claim 19.